/**
 * PHP控制下载速度
 *
 * @param 
 * @arrange 网： jb51.cc
 **/
// local file that should be send to the client
$local_file = 'test-file.zip';
// filename that the user gets as default
$download_file = 'your-download-name.zip';
// set the download rate limit (=> 20,5 kb/s)
$download_rate = 20.5;
if(file_exists($local_file) && is_file($local_file)) {
 // send headers
 header('Cache-control: private');
 header('Content-Type: application/octet-stream');
 header('Content-Length: '.filesize($local_file));
 header('Content-Disposition: filename='.$download_file);
 // flush content
 flush();
 // open file stream
 $file = fopen($local_file,"r");
 while (!feof($file)) {
 // send the current file part to the browser
 print fread($file,round($download_rate * 1024));
 // flush the content to the browser
 flush();
 // sleep one second
 sleep(1);
 }
 // close file stream
 fclose($file);
}
else {
 die('Error: The file '.$local_file.' does not exist!');
}
/***   来自编程之家 jb51.cc（jb51.cc）   ***/